Initial wireless communication systems have been developed to provide voice services while allowing the user to be mobile. Furthermore, the wireless communication systems have gradually provided data services as well as voice services, and recently, have advanced to provide a high-speed data service.
FIG. 1 illustrates a typical wireless communication system. Referring to FIG. 1, the wireless communication system may include a terminal 100, radio access networks (RAN) 125, 135, and 145, and core networks.
The radio access networks (RAN) 125, 135, and 145 have gradually changed over time. The terminal 100 has accessed radio access networks referred to as a GERAN (GSM EDGE radio access network) 145 and a UTRAN (Universal Terrestrial radio access network) 135 through a Um interface 118 and a Uu interface 114, respectively in the second and third generation communication systems. Currently, the terminal 100 may access a radio access network named E-UTRAN (Evolved-Universal Terrestrial radio access network) 125 through an LTE (Long Term Evolution)-Uu interface 110. The E-UTRAN 125 is generally referred to as LTE as well.
The E-UTRAN 125, the UTRAN 135, and the GERAN 145 are the networks comprised of a plurality of evolved nodes B (eNB) 120, a radio network subsystem (RNS) 130, and a base station subsystem (BSS) 140. For example, the E-UTRAN is a complicated network in which a plurality of evolved nodes B (eNB) 120 are connected. Each of the evolved Node B (eNB) 120, the radio network subsystem (RNS) 130, and the base station subsystem (BSS) 140 provides services to the terminal 100 in a specific range that is referred to as coverage. Since the coverage is limited, the terminal 100 should connect wirelessly to at least one of the evolved node B (eNB) 120, the radio network subsystem (RNS) 130, or the base station subsystem (BSS) 140 in order to use voice and/or data services while moving.
The radio network subsystem (RNS) 130 among the elements 120, 130, and 140 of the RANs (radio access networks) may be further divided into a node B (NB) and an RNC (Radio Network Controller). The base station subsystem (BSS) 140 may be further divided into a base transceiver station (BTS) and a base station controller (BSC). The node B (NB) and the base transceiver station (BTS) may be connected with the terminal 100 through wireless interfaces 114 and 118, and the radio network controller (RNC) and the base station controller (BSC) may be connected with the core network (CN) 180. The evolved node B (eNB) 120 may perform two functions. That is, one function is connecting to the terminal 100 through the wireless interface 110, and the other function is connecting to the evolved packet core (EPC) 160, which is a core network dedicated to the E-UTRAN.
With some exceptions, the evolved node B (eNB) 120, the node B (NB), and the base transceiver station (BTS) may be generally comprised of one or more cells. Here, the cell may refer to a cell in a typical cellular system, and the evolved node B (eNB) 120, the node B (NB) and the base transceiver station (BTS) may be devices for managing and controlling the cell. In the present specification, the evolved node B (eNB) 120, the node B (NB), and the base transceiver station (BTS) may be used as the same meaning for the convenience of explanation. In addition, in the description of the embodiments, the cells, the evolved node B (eNB) 120, the node B (NB), and the base transceiver station (BTS) may be interchangeably used with each other.
The evolved node B (eNB) 120 may be connected to a mobility management entity (MME) 150, which is one element of an evolved packet core (EPC) 160, through an S1-C interface 128. At this time, one or more mobility management entities 150a and 150b may be connected. Likewise, the radio network subsystem (RNS) 130 and the base station subsystem (BSS) 140 may be connected with a serving general packet radio service (GPRS) support node (SGSN) 170 through an Iu interface 173 and a Gb interface 175, respectively. The mobility management entity (MME) 150 and the serving general packet radio service support node (SGSN) 170 are elements for controlling the radio access network (RAN), and may perform the overall control, such as the mobility management, authentication, and security. In addition, they perform the calling and location management of the terminal in the idle mode.
Simply, it is typical that a single mobility management entity (MME) 150 manages a plurality of evolved nodes B (eNB) 120. However, the number of evolved nodes B (eNB) 120 that can be managed by a single mobility management entity (MME) 150 is limited, and the continuity of the service may be affected by the change of the mobility management entity (MME) 150. Therefore, the model in which a plurality of mobility management entities (MME) 150 manage a plurality of evolved nodes B (eNB) 120 has been introduced in order to provide services while securing smooth interworking over the wider coverage. In general, the number of mobility management entities (MMEs) 150 is much less than the number of evolved nodes B (eNB) 120. A group of a plurality of mobility management entities (MMEs) 150 is referred to as a mobility management entity (MME) pool.
The mobility management entities (MMEs) in the mobility management entity (MME) pool may be connected by an S10 interface 153. The mobility management entities (MMEs) in another mobility management entity (MME) pool may be connected by the S10 interface 153. The mobility management entities (MMEs) may transmit and receive necessary information through the S10 interface 153.
Although it is not shown in FIG. 1, the mobility management entity (MME) 150 and the serving general packet radio service support node (SGSN) 170 may be connected with each other. The terminal 100 may freely enter other radio access networks (RANs). For example, the terminal 100, which uses services in the UTRAN 135, may use services in the E-UTRAN 125. In this case, the mobility management entity (MME) 150 may make a request to the serving general packet radio service support node (SGSN) 170 for the necessary information, and the request may be transmitted through a connection between the mobility management entity (MME) 150 and the serving general packet radio service support node (SGSN) 170.
Furthermore, the mobility management entity (MME) 150 is connected with a home subscriber server (HSS) 155 through an S6a interface 158. The home subscriber server (HSS) 155 is a database server that has the overall information about the subscriber and user of the terminal 100. The mobility management entity (MME) 150 may make a request to the home subscriber server (HSS) 155 for necessary information and may receive the same. The necessary information may contain the mobility management, the call and session setup, the user authentication, or the access authorization.
In the wireless communication system, a small number of home subscriber servers (HSS) 155 are constructed. Therefore, the mobility management entity (MME) 150 frequently sends messages to the home subscriber server (HSS) 155 so that home subscriber server (HSS) 155 becomes overloaded and the performance of the entire wireless communication system may be degraded. Therefore, the authentication method of the system is required to be improved in order to solve the home subscriber server (HSS) overload problem and in order to enhance the performance of the entire wireless communication system.